Lean manufacturing focuses on constantly improving customer value while minimizing waste. There are five principles that are the guiding stars of the Lean management process.

- Identify value: Value includes everything that benefits the customer. You’ll need to distinguish value-adding benefits from wasteful processes.
- Map the value stream: Once you know what value the product brings to your customer, you’ll need to track its path through production to consumer.
- Create flow: A smooth flow has eliminated bottlenecks and waste from production processes.
- Establish pull: When your team has time and bandwidth, new work can be started. In a pull system, a task is only begun when there is capacity for the task to be completed.
- Continuously improve: Your customer’s perception of value will change over time, so your process must be constantly evolving to generate more and more value.

Waste in lean management is not just materials that are thrown away. It includes:

- Overproduction
- Over processing
- Unnecessary motion
- Unnecessary down time
- Untapped creativity

Consider the concept of unnecessary motion. If part of my process requires, for example, walking 10 steps and moving two levers when I could modify the process to need one step and one lever to produce the same outcome then I am wasting less motion (and time).

Cycle time reduction is achieved by reducing the time spent on non-value added activities and simplification and streamlining of the process; thereby reducing the cost of operations.

Takt calculation shows at what rate the customer will normally wish to have the product supplied. This is the basic starting point for all production rate calculations and is often referred to as rate-leveling. We want to avoid the ups and downs of normal production and rather stabilize the rate.

Takt Time = Demand Rate = Total available production time / Total production requirement

8-hour day = 480 min (8 x 60)

Customer demand = 160 pieces painted in a day

Average takt time = 480 minutes / 160 pieces = 3 minutes per piece

However, let’s say you have 2 shifts a day and a total of 50 minutes of break time for each shift (no machines are running during breaks). Then,

Available work time (production time) = 2 shifts x 480 min per shift – (2 shifts x 50 min breaks) =

Available work time (production time) = 960 minutes – 100 minutes = 860

Customer demand remains at 160 pieces painted per day. This makes

Takt time in scenario 2 = 860 minutes /160 pieces = 5.375 minutes per piece.

Availability is the percentage of time available to run the machine within a shift after losses due to setups and breakdowns. It is calculated by recording the time lost due to breakdowns (unplanned stoppages of more than 10 minutes) in minutes and the time lost during setup (Last good part of one product to the first good part of the next) also in minutes, we then compare this to the total available time within the shift.

Example:

We have one machine that is run by multiple employees who take breaks at alternating times so as to not affect
machine operations/availability. A shift is 8 hours long and we have 10 minutes allocated for maintenance work
and machine cleaning each shift. Therefore we have 8 x 60 – 10 minutes or 470 minutes maximum available time.

If we lose an hour of production, 20 minutes due to breakdowns and 40 minutes for setups then our percentage availability is:

Availability = ((Total time available – Breakdowns – Changeover)/Total time available) x 100

Availability = ((470 minutes–20 minute breakdown–40 minute changeover)/470 minutes) x 100 = 87.2%

(Lean Manufacturing Tools, n.d.)

Process/Production Capacity

Process/production capacity to the production capacity of workers or machines. It is the maximum amount of output that can be obtained through a certain machine or production line. Capacity can also be expressed in terms of an output rate of a certain number of units per unit of time.

Capacity = Operational time per shift / (Process time + Setup time per interval)

you may also see it written as:

Capacity = Available time per shift / (Total cycle time per piece + Tool change time per piece)

Caveat note: Certain machinery and plants can attain peak capacity, this is the maximum output amount, but it cannot be sustained for long periods of time or with a greater amount of resources. Capacity assumes a constant level of maximum output.

An example if there are three identical machines that all produce a widget (no change time necessary and efficiency is 100%)

Number of machines available: 3

Hours they are operated: 8 a.m. to 6 p.m. (10 hours a day)

Machine hour capability: 3 x 10 = 30 hours a day

Time required to produce 1 widget: 30 min (.5 hours)

Capacity is therefore: 30 / .5 = 60 widgets

Kaizen Institute. (n.d.). What is Kaizen. Retrieved July 15, 2021 from https://www.kaizen.com/what-is-kaizen.html

Koo, J. (2020). Push System vs. Pull System. Tulip. Retrieved July 15, 2021 from https://tulip.co/blog/what-is-a-push-system-vs-a-pull-system/

Lean Manufacturing Tools (n.d.) OEE Calculation. Retrieved August 1, 2021 from https://leanmanufacturingtools.org/443/oee-calculation/

Lucidchart. (n.d.). The Best Lean Tools for Process Improvement. Retrieved July 9, 2021 from https://www.lucidchart.com/blog/best-lean-tools-for-process-improvement

Munro, R., Ramu, G., & Zrymiak, D. (2015). The Certified Six Sigma Green Belt Handbook. Retrieved July 12, 2021 from https://www.academia.edu/40442176/The_Certified_Six_Sigma_Green_Belt_Handbook_Second_Edition

©2021 - Dr. Anne Arendt